The U.S. Food and Drug Administration said Thursday it asked manufacturers of Permax, a drug used to treat Parkinson's Disease, to withdraw it from the market because it's linked to heart-valve problems.

Eli Lilly & Co. sells brand-name Permax, and FDA said officials at least two other firms sell a generic version.

The drug has carried a "black box" warning about the heart-valve problems and use of the product has been steadily declining since then.

The agency said it decided to ask Permax makers to withdraw the drug because similar drugs used to treat Parkinson's do not carry the heart-valve risk. The agency estimates that fewer than 25,000 people use Permax or a generic version.